JP7217320B2 - Material for organic electroluminescence device and organic electroluminescence device - Google Patents

Description

The present invention relates to a compound and an organic EL device suitable for an organic electroluminescence device (hereinafter sometimes referred to as an organic EL device) suitable for various display devices. It relates to an organic EL element.

Organic EL elements are self-luminous elements, and are brighter than liquid crystal elements, have excellent visibility, and are capable of displaying clear images, and have been actively studied.

In recent years, as an attempt to increase the luminous efficiency of a device, a device has been developed in which a phosphorescent emitter is used to generate phosphorescence, that is, a device utilizing light emission from a triplet excited state. According to the theory of the excited state, when phosphorescence is used, a significant improvement in luminous efficiency is expected, which is about four times the luminous efficiency of conventional fluorescent luminescence. In 1993, M.D. at Princeton University. A. Baldo et al. achieved an external quantum efficiency of 8% with a phosphorescent device using an iridium complex.

In an organic EL device, carriers are injected into a light-emitting substance from both positive and negative electrodes to generate a light-emitting substance in an excited state to emit light. Generally, in the case of this carrier injection type organic EL element, it is said that 25% of the generated excitons are excited to the excited singlet state, and the remaining 75% are excited to the excited triplet state. ing. Therefore, it is considered that the use of phosphorescence, which is light emission from the excited triplet state, is more efficient in energy utilization. However, since phosphorescence has a long lifetime in the excited triplet state, energy deactivation occurs due to saturation of the excited state and interaction with excitons in the excited triplet state. Therefore, the phosphorescence quantum yield of phosphorescent emitters is generally not high in many cases.

In order to solve such problems, it is conceivable to use a delayed fluorescence material that exhibits delayed fluorescence. After energy transition to an excited triplet state due to intersystem crossing, some fluorescent substances undergo reverse intersystem crossover to an excited singlet state due to triplet-triplet annihilation or absorption of thermal energy, and fluoresce. radiate. The latter, that is, thermally activated delayed fluorescence materials, are considered particularly useful in organic EL devices.

In fact, in recent years, devices utilizing light emission by thermally activated delayed fluorescence (TADF) have also been developed. In 2011, Adachi et al. of Kyushu University realized an external quantum efficiency of 5.3% with a device using a thermally activated delayed fluorescence material.

When a thermally activated delayed fluorescence material is used in an organic EL device, excitons in the excited singlet state emit normal fluorescence (immediate fluorescence). On the other hand, excitons in the excited triplet state absorb the heat generated by the device and undergo reverse intersystem crossover to the excited singlet state to emit delayed fluorescence. Since this delayed fluorescence is emitted from the excited singlet, it has the same wavelength as the immediate fluorescence. longer than Therefore, it is observed as delayed fluorescence rather than immediate fluorescence or phosphorescence. By using such a thermally activated exciton transfer mechanism, that is, by undergoing thermal energy absorption after carrier injection, the ratio of excitons in the excited singlet state, which was normally generated only 25%, was reduced to 25%. % can be increased. For example, if a compound that emits strong fluorescence and delayed fluorescence even at a low temperature of less than 100 ° C. is used, the heat of the device causes sufficient reverse intersystem crossing from the excited triplet state to the excited singlet state, and delayed fluorescence is emitted. do. This dramatically improves the luminous efficiency of the organic EL device (Patent Documents 1 and 2).

In the organic EL device, charges injected from both electrodes are recombined in the light-emitting layer to obtain light emission. Therefore, in an organic EL device, it is important how efficiently both the charges of holes and electrons are transferred to the light-emitting layer. In addition to improving the hole injection property into the light emitting layer, the probability of recombination of holes and electrons is improved by improving the electron blocking property of blocking electrons injected from the cathode on the anode side of the light emitting layer, and further High luminous efficiency can be obtained by confining the generated excitons in the light-emitting layer. Therefore, the role played by a hole-transporting material that has hole-transporting properties and is used for forming a hole-injecting layer, a hole-transporting layer, an electron-blocking layer, or a light-emitting layer is important. Hole transport materials are required to have high hole mobility, high hole injection properties, high electron blocking properties, high triplet energy, and high durability against electrons. ing.

Also, heat resistance and amorphousness of the material are important for the lifetime of the device. A material with low heat resistance undergoes thermal decomposition even at a low temperature due to the heat generated when the device is driven, and the material deteriorates. In addition, with materials having low amorphous properties, crystallization of the thin film occurs even for a short period of time, resulting in deterioration of the device. Therefore, the material to be used is required to have high heat resistance and good amorphous properties.

Until now, N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (NPD) and various aromatic amine derivatives have been known as hole-transporting materials for organic EL devices (Patent Document 1 and Patent Document 2). NPD exhibits good hole-transporting properties, but its glass transition point (Tg), which is an index of heat resistance, is as low as 96° C. Under high-temperature conditions, crystallization causes degradation of device characteristics. In addition, among the aromatic amine derivatives described in Patent Document 1 and Patent Document 2, there are compounds having excellent hole mobility of 10 ⁻³ cm ² /Vs or more, but electron blocking properties is insufficient. Therefore, in an organic EL device formed using such an aromatic amine derivative, some electrons pass through the light-emitting layer, and improvement in light-emitting efficiency cannot be expected. Therefore, in order to further improve the efficiency, there has been a demand for a material that has a higher electron-blocking property, a more stable thin film, and a higher heat resistance.

As a compound having improved properties such as heat resistance, hole injection properties, hole transport properties, and electron blocking properties, an aromatic tertiary amine compound A represented by the following formula has been proposed (Patent Document 3).

However, devices using this compound A for the hole injection layer, the hole transport layer or the electron blocking layer have been improved in heat resistance and luminous efficiency, but are still not sufficient. In addition, there is room for improvement in driving voltage and current efficiency, and there is also a problem with amorphousness. Furthermore, Patent Document 3 does not describe or suggest a case where a delayed fluorescence material is used as a light-emitting material in an organic EL device using this compound.

Indenocarbazole derivatives represented by the following formula (Y) have also been proposed as compounds having electron-transporting properties and hole-transporting properties (Patent Document 4).

However, according to Patent Document 4, an organic EL device using this compound in the electron blocking layer shows only a slight improvement in power efficiency. In addition, there is no description of an organic EL device using this compound and using a thermally activated delayed fluorescent material as a dopant material for the light-emitting layer.

In this way, in order to improve the element characteristics of the organic EL element, it is necessary to improve the hole transportability, the hole injection property, the electron blocking property, the stability of the thin film state, etc., and the organic EL element that emits delayed fluorescence. There is a need for compounds that can be used as pore transport materials.

JP 2004-241374 A JP 2006-024830 A WO2012/117973 WO2010/136109

Appl. Phys. Let. , 98, 083302 (2011) Appl. Phys. Let. , 101, 093306 (2012) Chem. Commun. , 48, 11392 (2012) NATURE 492, 235 (2012)

An object of the present invention is to provide a material having a hole-transporting property and suitable for use in forming an organic EL device, particularly a hole-transporting layer and a hole-injecting material when a delayed fluorescence material is used as a dopant material in the light-emitting layer. As a material suitable for the layer or the electron blocking layer, an indenocarbazole compound having (1) excellent hole transport properties, (2) excellent electron blocking properties, and (3) a stable thin film state and excellent heat resistance is used. to provide.

Another object of the present invention is to provide an organic EL device with high luminous efficiency and high brightness.

In order to achieve the above objects, the present inventors have found that an indenocarbazole derivative having a specific structure has hole-transport properties, excellent thin film stability and durability, and a minimum triplet state (T ₁ ). We paid attention to the high energy level. Therefore, various indenocarbazole compounds were designed and synthesized, and their physical properties were evaluated. As a result, an indenocarbazole compound in which a specific position is substituted with an aromatic hydrocarbon group, an aromatic heterocyclic group, or a disubstituted amino group substituted with an aromatic hydrocarbon group or an aromatic heterocyclic group has hole-transporting properties. , electron blocking properties, thin film state stability and heat resistance.

Furthermore, various organic EL devices were produced using the indenocarbazole compounds, and the characteristics of the devices were evaluated. As a result, the present invention was completed.

式中、
Ｒ^１～Ｒ^１２は、同一でも異なってもよく、水素原子；重水素原子；
フッ素原子；塩素原子；シアノ基；ニトロ基；炭素数１～８のアルキル
基；炭素数５～１０のシクロアルキル基；炭素数２～６のアルケニル基
；炭素数１～６のアルキルオキシ基；炭素数５～１０のシクロアルキル
オキシ基；芳香族炭化水素基；芳香族複素環基；アリールオキシ基；ま
たは芳香族炭化水素基もしくは芳香族複素環基によって置換されたジ置
換アミノ基；を表し、Ｒ^１～Ｒ^１２は、単結合、置換もしくは無置換の
メチレン基、酸素原子または硫黄原子を介して結合して環を形成しても
よく、
Ｘは、芳香族炭化水素基；芳香族複素環基；または芳香族炭化水素基
もしくは芳香族複素環基によって置換されたジ置換アミノ基；を表す。 That is, according to the present invention, there is provided an indenocarbazole compound which has a hole-transporting property, is used as a constituent material of an organic electroluminescence device, and is represented by the following general formula (1). be done.

During the ceremony,
R ¹ to R ¹² may be the same or different, hydrogen atom; deuterium atom;
Fluorine atom; chlorine atom; cyano group; nitro group; alkyl group having 1 to 8 carbon atoms; cycloalkyl group having 5 to 10 carbon atoms; C5-C10 cycloalkyloxy groups; aromatic hydrocarbon groups; aromatic heterocyclic groups; aryloxy groups; or disubstituted amino groups substituted by aromatic hydrocarbon groups or aromatic heterocyclic groups and R ¹ to R ¹² may be bonded via a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring,
X represents an aromatic hydrocarbon group; an aromatic heterocyclic group; or a disubstituted amino group substituted with an aromatic hydrocarbon group or an aromatic heterocyclic group.

式中、
Ｒ^１～Ｒ^１２およびＸは前記一般式（１）に記載した通りの意味であ
る。
２）Ｒ^１～Ｒ^１２で表される炭素数１～８のアルキル基が、炭素数１～６のアルキル基であること。
３）Ｘが、芳香族複素環基またはジ置換アミノ基であること。
４）Ｘが、含窒素芳香族複素環基であること。 Preferred embodiments of the indenocarbazole compound of the present invention are as follows.
1) Represented by the following general formula (1-1).

During the ceremony,
R ¹ to R ¹² and X have the same meanings as described in formula (1) above.
2) The C 1-8 alkyl groups represented by R ¹ to R ¹² are C 1-6 alkyl groups.
3) X is an aromatic heterocyclic group or a disubstituted amino group;
4) X is a nitrogen-containing aromatic heterocyclic group;

In this specification, unless otherwise specified, R ¹ to R ¹² and X represent alkyl groups having 1 to 8 carbon atoms, cycloalkyl groups having 5 to 10 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, and Alkyloxy groups having 1 to 6 carbon atoms, cycloalkyloxy groups having 5 to 10 carbon atoms, aromatic hydrocarbon groups, aromatic heterocyclic groups and aryloxy groups may be substituted or unsubstituted. may In addition, the aromatic hydrocarbon group or aromatic heterocyclic group which the disubstituted amino group represented by R ¹ to R ¹² and X has as a substituent may further have a substituent or may be unsubstituted. may

Aliphatic hydrocarbon groups such as alkyl groups, alkenyl groups and alkyloxy groups may be linear or branched unless otherwise specified. Unless otherwise specified, the aromatic hydrocarbon group and the aromatic heterocyclic group may have a monocyclic structure, a polycyclic structure, or a condensed polycyclic structure.

Further, according to the present invention, in an organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched therebetween, the indenocarbazole compound is used as a constituent material of at least one organic layer. An organic electroluminescence device characterized by the following is provided.

In the organic electroluminescence of the present invention,
5) the organic layer is a hole transport layer, an electron blocking layer, a hole injection layer or a light emitting layer;
6) emitting delayed fluorescence;
is preferred.

Further, according to the present invention, in the organic electroluminescence device having a light-emitting layer selectively between a pair of electrodes, the indenocarbazole compound is used as a constituent material of the light-emitting layer. An organic electroluminescent device is provided. The organic electroluminescence of this aspect preferably emits delayed fluorescence.

Further, according to the present invention, in the organic electroluminescence device having a light emitting layer and another layer between a pair of electrodes, the other layer is a hole injection layer, a hole transport layer or an electron blocking layer. and an organic electroluminescence device, wherein the indenocarbazole compound is used as a constituent material of the light-emitting layer or the other layer. The organic electroluminescence of this aspect preferably emits delayed fluorescence.

The indenocarbazole compound of the present invention has a high lowest triplet state (T ₁ ) energy level and a wide HOMO-LUMO bandgap. Therefore, it has a hole-transport property and has one or more of the following properties.
(1) Higher hole mobility and higher hole transportability than conventional materials.
(2) High hole injection properties.
(3) High electron blocking properties.
(4) High stability to electrons.
In addition, the thin film state is stable, and the heat resistance is also excellent. Due to such properties, the indenocarbazole compound of the present invention is suitable as a material for organic EL devices. It can also be used as a material for organic photoluminescence elements.

Also, the organic EL device of the present invention using such an indenocarbazole compound has the following characteristics.
(5) High luminous efficiency.
(6) Brightness is high.
(7) Light emission start voltage is low.
(8) Practical drive voltage is low.
(9) Low manufacturing cost.

The indenocarbazole compound of the present invention is suitably used as a constituent material for the hole injection layer or hole transport layer of an organic EL device. In an organic EL device having a hole-injecting layer or a hole-transporting layer prepared using the indenocarbazole compound of the present invention, excitons generated in the light-emitting layer can be confined, and holes and electrons can be confined. It is possible to improve the probability of recombination and obtain high luminous efficiency. In addition, the driving voltage is low and the durability is excellent.

Moreover, the indenocarbazole compound of the present invention is also suitably used as a constituent material of an electron blocking layer of an organic EL device. This is because such an indenocarbazole compound has excellent electron blocking properties, excellent hole transport properties, and high stability in a thin film state. An organic EL device having an electron-blocking layer prepared using the indenocarbazole compound of the present invention has high luminous efficiency, low driving voltage, excellent current resistance, and high maximum emission luminance.

Furthermore, the indenocarbazole compound of the present invention is also suitably used as a constituent material for the light-emitting layer of an organic EL device. Such an indenocarbazole compound has excellent hole-transport properties and a wide bandgap. Therefore, the indenocarbazole compound of the present invention is used as a host material for the light-emitting layer, and a fluorescent light emitter, a phosphorescent light emitter, or a delayed fluorescent material called a dopant is supported to form the light-emitting layer, thereby reducing the driving voltage. It is possible to realize an organic EL device with a low V and improved luminous efficiency.

As described above, the use of the indenocarbazole derivative of the present invention makes it possible to obtain an organic EL device with improved properties. Furthermore, by using a delayed fluorescence material as a dopant material in the light-emitting layer of the organic EL device of the present invention, the use of light-emitting materials containing rare metals such as iridium and platinum can be avoided. That is, since scarce and expensive rare metals are not used, in the organic EL device of the present invention, the combined use of the indenocarbazole compound and the delayed fluorescence material provides an organic EL device that is advantageous in terms of resources and cost in addition to the above effects. element can be realized.

1 is a ¹ H-NMR chart of Compound 1 of Example 1. FIG. 1 is a ¹ H-NMR chart of Compound 2 of Example 2. FIG. 1 is a ¹ H-NMR chart of Compound 3 of Example 3. FIG. 1 is a ¹ H-NMR chart of Compound 24 of Example 4. FIG. FIG. 2 is a diagram showing organic EL device configurations of Device Examples 1 to 4 and Device Comparative Example 1; 1 is a diagram showing structural formulas of compounds 1 to 8, which are indenocarbazole compounds of the present invention. FIG. FIG. 2 shows structural formulas of compounds 9 to 16, which are indenocarbazole compounds of the present invention. FIG. 2 shows structural formulas of compounds 17 to 24, which are indenocarbazole compounds of the present invention. FIG. 2 shows structural formulas of compounds 25 to 36, which are indenocarbazole compounds of the present invention. FIG. 2 shows structural formulas of compounds 37 to 45, which are indenocarbazole compounds of the present invention.

<Indenocarbazole compound>
The indenocarbazole compound of the present invention is represented by the following general formula (1).

The indenocarbazole compound represented by the above general formula (1) includes embodiments represented by the following general formula (1-1). This embodiment specifies the binding positions of X, R ² to R ⁹ and R ¹² in general formula (1).

(R ¹ to R ¹² )
R ¹ to R ¹² may be the same or different, hydrogen atom; deuterium atom; fluorine atom; chlorine atom; cyano group; nitro group; alkyl group having 1 to 8 carbon atoms; group; alkenyl group having 2 to 6 carbon atoms; alkyloxy group having 1 to 6 carbon atoms; cycloalkyloxy group having 5 to 10 carbon atoms; aromatic hydrocarbon group; aromatic heterocyclic group; a disubstituted amino group substituted with a group selected from a hydrocarbon group or an aromatic heterocyclic group;

R ¹ to R ¹² may exist independently and do not form a ring, but form a ring by bonding to each other through a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom You may When R ¹ to R ¹² are disubstituted amino groups, the aromatic hydrocarbon group or aromatic heterocyclic group in the disubstituted amino group contributes to ring formation.

Specific examples of the alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 10 carbon atoms or alkenyl group having 2 to 6 carbon atoms represented by R ¹ to R ¹² include methyl group, ethyl group, n -propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, n-octyl group, etc.; cyclopentyl group, cyclohexyl group, 1- adamantyl group, 2-adamantyl group; vinyl group, allyl group, isopropenyl group, 2-butenyl group; As the alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms is preferable.

An alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms or an alkenyl group having 2 to 6 carbon atoms represented by R ¹ to R ¹² may be unsubstituted, but may have a substituent. good too. Examples of substituents include deuterium atoms, cyano groups, nitro groups, and the following groups.
halogen atoms, such as fluorine atoms, chlorine atoms, bromine atoms, iodine atoms;
an alkyloxy group having 1 to 6 carbon atoms, such as a methyloxy group, an ethyloxy group, a propyloxy group;
an aryloxy group, such as a phenyloxy group, a tolyloxy group;
arylalkyloxy groups, such as benzyloxy groups, phenethyloxy groups;
aromatic hydrocarbon groups such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenanthrenyl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl,
a triphenylenyl group;
Aromatic heterocyclic groups such as pyridyl, pyrimidinyl, triazinyl, thienyl, furyl, pyrrolyl, quinolyl, isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, benzoxazolyl, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbolinyl group;
These substituents may be unsubstituted, or may be further substituted with the substituents exemplified above. These substituents may exist independently and may not form a ring, but may be bonded to each other through a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring. may be formed.

Specific examples of the alkyloxy group having 1 to 6 carbon atoms or the cycloalkyloxy group having 5 to 10 carbon atoms represented by R ¹ to R ¹² include methyloxy group, ethyloxy group, n-propyloxy group and isopropyl oxy group, n-butyloxy group, tert-butyloxy group, n-pentyloxy group, n-hexyloxy group, cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, cyclooctyloxy group, 1-adamantyloxy group, 2 -adamantyloxy group and the like.

The alkyloxy group having 1 to 6 carbon atoms or the cycloalkyloxy group having 5 to 10 carbon atoms represented by R ¹ to R ¹² may be unsubstituted or may have a substituent. As the substituent, the substituent that may be possessed by the alkyl group having 1 to 8 carbon atoms, the cycloalkyl group having 5 to 10 carbon atoms or the alkenyl group having 2 to 6 carbon atoms represented by R ¹ to R ¹² Examples similar to those shown can be mentioned. Possible modes are also the same.

Specific examples of aromatic hydrocarbon groups or aromatic heterocyclic groups represented by R ¹ to R ¹² include phenyl group, biphenylyl group, terphenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, fluorenyl group and indenyl group. , pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group, pyridyl group, pyrimidinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, indenocarbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzazepinyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group , phenazinyl group, phenoxazinyl group, phenoselenazinyl group, phenothiazinyl group, phenothelazinyl group, phenophosphinazinyl group, acridinyl group, carbolinyl group and the like.

The aromatic hydrocarbon group or aromatic heterocyclic group represented by R ¹ to R ¹² may be unsubstituted or may have a substituent. Examples of substituents include deuterium atoms, cyano groups, nitro groups, and the following groups.
halogen atoms, such as fluorine atoms, chlorine atoms, bromine atoms, iodine atoms;
Alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n- hexyl group;
an alkyloxy group having 1 to 6 carbon atoms, such as a methyloxy group, an ethyloxy group, a propyloxy group;
alkenyl groups having 2 to 6 carbon atoms, such as vinyl groups and allyl groups;
an aryloxy group, such as a phenyloxy group, a tolyloxy group;
arylalkyloxy groups, such as benzyloxy groups, phenethyloxy groups;
aromatic hydrocarbon groups such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl, phenanthrenyl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl,
a triphenylenyl group;
aromatic heterocyclic groups such as pyridyl, pyrimidinyl, triazinyl, furyl, thienyl, pyrrolyl, quinolyl, isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, indenocarba zolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbolinyl group, phenoxazinyl group, phenothiazinyl group, acridinyl group, phenazinyl group;
aryl vinyl groups, such as styryl groups, naphthyl vinyl groups;
an acyl group, such as an acetyl group, a benzoyl group;
disubstituted amino groups, e.g., dialkylamino groups substituted with alkyl groups such as dimethylamino group and diethylamino group;
disubstituted amino groups substituted only with aromatic hydrocarbon groups such as diphenylamino groups and dinaphthylamino groups;
dialkylamino groups substituted with aralkyl groups such as dibenzylamino group and diphenethylamino group;
a disubstituted amino group substituted only with an aromatic heterocyclic group such as a dipyridylamino group or a dithienylamino group;
a dialkenylamino group substituted with an alkenyl group such as a diallylamino group;
Disubstituted amino groups substituted with other substituents selected from the group consisting of alkyl groups, aromatic hydrocarbon groups, aralkyl groups, aromatic heterocyclic groups and alkenyl groups;
These substituents may be unsubstituted, or may be further substituted with the substituents exemplified above. These substituents may exist independently and may not form a ring, but may be bonded to each other through a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring. may be formed. When the above substituent is a disubstituted amino group, the alkyl group, aromatic hydrocarbon group, aralkyl group, aromatic heterocyclic group or alkenyl group that constitutes the disubstituted amino group contributes to ring formation.

Specific examples of the aryloxy groups represented by R ¹ to R ¹² include a phenyloxy group, a biphenylyloxy group, a terphenylyloxy group, a naphthyloxy group, an anthracenyloxy group and a phenanthrenyloxy group. , fluorenyloxy group, indenyloxy group, triphenylenyloxy group, pyrenyloxy group, perylenyloxy group and the like.

The aromatic hydrocarbon group or aromatic heterocyclic group represented by R ¹ to R ¹² may be unsubstituted or may have a substituent. As the substituent, the same substituents as those described above for the substituent which the aromatic hydrocarbon group or the aromatic heterocyclic group represented by R ¹ to R ¹² may have can be mentioned. Possible modes are also the same.

The aromatic hydrocarbon group or aromatic heterocyclic group which the disubstituted amino group represented by R ¹ to R ¹² has as a substituent includes the aromatic hydrocarbon group or aromatic heterocyclic group represented by R ¹ to R ¹² above. The same examples as those given for the heterocyclic group can be mentioned.

The aromatic hydrocarbon group or aromatic heterocyclic group which the disubstituted amino group represented by R ¹ to R ¹² has as a substituent may be unsubstituted or may further have a substituent. As the substituent, the same substituents as those described above for the substituent which the aromatic hydrocarbon group or the aromatic heterocyclic group represented by R ¹ to R ¹² may have can be mentioned. Possible modes are also the same.

(X)
X represents an aromatic hydrocarbon group, an aromatic heterocyclic group, or a disubstituted amino group substituted with an aromatic hydrocarbon group or an aromatic heterocyclic group.

Examples of the aromatic hydrocarbon group or aromatic heterocyclic group represented by X include the same groups as those described above for R ¹ to R ¹² .

The aromatic hydrocarbon group or aromatic heterocyclic group represented by X may be unsubstituted or may have a substituent. As the substituent, the same substituents as those described above for the substituent which the aromatic hydrocarbon group or the aromatic heterocyclic group represented by R ¹ to R ¹² may have can be mentioned. Possible modes are also the same.

As the aromatic hydrocarbon group or aromatic heterocyclic group which the disubstituted amino group represented by X has as a substituent, the aromatic hydrocarbon group or aromatic heterocyclic group represented by R ¹ to R ¹² Examples similar to those shown can be mentioned.

The aromatic hydrocarbon group or aromatic heterocyclic group which the disubstituted amino group represented by R ¹ to R ¹² has as a substituent may be unsubstituted or may further have a substituent. As the substituent, the same substituents as those described above for the substituent which the aromatic hydrocarbon group or the aromatic heterocyclic group represented by R ¹ to R ¹² may have can be mentioned. Possible modes are also the same.

(preferred embodiment)
Preferred embodiments of the indenocarbazole compound are described below.
As the indenocarbazole compound, an indenocarbazole compound represented by the general formula (1-1) is preferable.

R ¹ is preferably an aromatic hydrocarbon group or an aromatic heterocyclic group, an aromatic hydrocarbon group having no condensed polycyclic structure or an aromatic group having a condensed polycyclic structure and having no nitrogen atom as a heteroatom Group heterocyclic groups are more preferred. Moreover, the aromatic heterocyclic group having no nitrogen atom as a hetero atom is preferably an oxygen-containing aromatic heterocyclic group. Specifically, a phenyl group, a biphenylyl group, a terphenylyl group, a benzofuranyl group, a benzothienyl group, a dibenzofuranyl group or a dibenzothienyl group is preferred, and a phenyl group, a biphenylyl group or a dibenzofuranyl group is more preferred. The group represented by R ¹ is preferably unsubstituted.

R ² to R ⁹ and R ¹² are preferably a hydrogen atom or a deuterium atom, more preferably a hydrogen atom.

R ¹⁰ and R ¹¹ are preferably an alkyl group having 1 to 8 carbon atoms or an aromatic hydrocarbon group, more preferably a methyl group, an octyl group or a phenyl group, particularly preferably a methyl group.

X is preferably an aromatic heterocyclic group or a disubstituted amino group, more preferably an aromatic heterocyclic group, particularly preferably a nitrogen-containing aromatic heterocyclic group, a nitrogen-containing aromatic having a condensed polycyclic structure of 3 or more rings heterocyclic groups are most preferred. Specifically, a phenoxazinyl group, a phenothiazinyl group, an acridinyl group, a phenazinyl group, a carbazolyl group, an indenocarbazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a phenanthrolinyl group or a carbolinyl group is preferred, and dibenzofuran A nyl group, a carbazolyl group or an indenocarbazolyl group is more preferred.
In addition, these aromatic heterocyclic groups preferably have an N atom on the aromatic heterocyclic ring bonded to the indenocarbazole skeleton in terms of ease of production, power efficiency, brightness, and the like. From the viewpoint of device life, a nitrogen-containing aromatic heterocyclic group having a condensed polycyclic structure of three or more rings, such as a carbazolyl group or an indenocarbazolyl group, is preferable. An aromatic heterocyclic group having a condensed polycyclic structure of rings or more and having no nitrogen atom as a hetero atom, such as a dibenzothienyl group or a dibenzofuranyl group, is preferred, and a dibenzofuranyl group is more preferred.
Here, the dibenzofuranyl group and the dibenzothienyl group are preferably unsubstituted.
A phenoxazinyl group, a phenothiazinyl group, an acridinyl group, a phenazinyl group, a carbazolyl group, an indenocarbazolyl group, a phenanthrolinyl group, or a carbolinyl group is unsubstituted or has a substituent, and a substituent As, an alkyl group having 1 to 4 carbon atoms; an aromatic hydrocarbon group; an aromatic heterocyclic group; more preferably amino group, biphenylyl group, fluorenyl group, indenocarbazolyl group, dibenzothienyl group or dibenzofuranyl group, methyl group, phenyl group, carbazolyl group, biphenylyl group, fluorenyl group, indenocarbazolyl group, A dibenzothienyl group or a dibenzofuranyl group is particularly preferred, and a methyl group is most preferred.

Preferred specific examples of the indenocarbazole compound of the present invention are shown in FIGS. 6 to 10, but the indenocarbazole compound is not limited to these compounds. D represents a deuterium atom.

Among specific examples, compounds 1, 4 to 6, and 9 to 23 have two or more indenocarbazole structures in one molecule, and the indenocarbazole structure drawn on the rightmost side of the paper is the indenocarbazole compound of the present invention. corresponds to the main skeleton of

Compounds 1 to 45 in the specific examples all correspond to the above general formula (1-1).

<Manufacturing method>
The indenocarbazole compound of the present invention can be produced by known methods. For example, it can be synthesized by performing a condensation reaction such as a Buchwald-Hartwig reaction between an indenocarbazole substituted with a halogen such as bromine and an amine such as a nitrogen-containing heterocycle in the presence of a base.
Specifically, first, in the presence of a palladium catalyst and a base, an indenocarbazole derivative and a halide such as an aryl halide or a heteroaryl halide are subjected to a Buchwald-Hartwig reaction to obtain a compound corresponding to R ¹ in the above general formula (1). Synthesize an indenocarbazole derivative into which a group is introduced. Next, the obtained indenocarbazole derivative is halogenated using NBS or the like. Subsequently, the above general formula ( A group corresponding to X in 1) is introduced.

Purification of the indenocarbazole compound can be carried out by purification by column chromatography, adsorption purification by silica gel, activated carbon, activated clay or the like, recrystallization or crystallization with a solvent, or the like. Purification by a sublimation purification method or the like may be performed. Identification of compounds can be performed by NMR analysis. As physical property values, a glass transition point (Tg), a work function, and the like can be measured.

The glass transition point (Tg) is an index of the stability of the thin film state. The glass transition point (Tg) can be measured using a powder with a high-sensitivity differential scanning calorimeter (DSC3100S, manufactured by Bruker AXS).

The work function is an index of hole transportability. The work function can be obtained by forming a thin film of 100 nm on an ITO substrate and using an ionization potential measurement device (manufactured by Sumitomo Heavy Industries, Ltd., model PYS-202).

The indenocarbazole compound of the present invention has a hole-transporting property and exhibits a work function of 5.5 eV or more exhibited by conventionally known hole-transporting materials such as NPD and TPD.

<Organic EL element>
The indenocarbazole compound of the present invention described above is used as a constituent material of an organic EL device. Specifically, in an organic EL device having a structure comprising a pair of electrodes and at least one organic layer sandwiched between them, the indenocarbazole compound of the present invention is used as a constituent material of at least one organic layer. be done.

As long as these conditions are satisfied, the layer structure of the organic EL device of the present invention can take various forms. For example, a mode in which only a light-emitting layer is selectively provided between a pair of electrodes can be adopted. Alternatively, a mode in which a light-emitting layer and another layer (a hole injection layer, a hole transport layer, or an electron blocking layer) are provided between a pair of electrodes can be adopted. A specific example of a mode in which a light emitting layer and other layers are provided includes a structure in which an anode, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode are sequentially provided on a substrate. A hole injection layer may be provided between the anode and the hole transport layer. An electron blocking layer may be provided between the light emitting layer and the hole transport layer. A hole-blocking layer may be provided between the light-emitting layer and the electron-transporting layer. An exciton blocking layer may be provided on the anode side or the cathode side of the light-emitting layer. Furthermore, it is possible to omit or combine some of the organic layers. For example, it is possible to have a structure that serves both as a hole injection layer and a hole transport layer, or a structure that serves as both an electron transport layer and an electron injection layer. Moreover, it is possible to have a structure in which two or more organic layers having the same function are laminated. For example, a configuration in which two hole transport layers are stacked, a configuration in which two light emitting layers are stacked, a configuration in which two electron transport layers are stacked, and the like are possible. FIG. 5 shows the layer structure employed in the examples described later. Specifically, a transparent anode 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9 and a cathode 10 are formed on a glass substrate 1. are formed in this order.

<Anode>
The anode 2 may be made of an electrode material known per se, and for example, an electrode material with a large work function such as ITO or gold is used.

<Hole injection layer>
The indenocarbazole compound of the present invention can be suitably used for the hole injection layer 3 . In addition, known materials may be used instead of the indenocarbazole compound of the present invention, mixed with or used simultaneously with the indenocarbazole compound of the present invention.

Examples of known materials include porphyrin compounds typified by copper phthalocyanine; naphthalenediamine derivatives; starburst-type triphenylamine derivatives; A triphenylamine trimer or tetramer having a structure; an acceptor heterocyclic compound such as hexacyanoazatriphenylene; a coating type polymer material; and the like can be used.

In addition to the materials normally used for the hole injection layer, P-doped trisbromophenylamine hexachloroantimony, radialene derivatives (WO2014/009310) and the like, and the structure of benzidine derivatives such as TPD are added to the partial structure. It is possible to use a polymer compound having

The hole injection layer 3 can be obtained by forming a thin film using these materials by a known method such as a vapor deposition method, a spin coating method, or an inkjet method. Each layer described below can be similarly obtained by forming a thin film by a known method such as a vapor deposition method, a spin coating method, an inkjet method, or the like.

<Hole transport layer>
The indenocarbazole compound of the present invention can be suitably used for the hole transport layer 4 . In addition, known materials exemplified below may be used instead of the indenocarbazole compound of the present invention, mixed with the indenocarbazole compound of the present invention, or used simultaneously.
compounds containing an m-carbazolylphenyl group;
benzidine derivatives such as N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (
TPD),
N,N'-diphenyl-N,N'-di(α-naphthyl)-benzidine (NPD),
N,N,N',N'-tetrabiphenylylbenzidine;
1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (
TAPC);
various triphenylamine trimers and tetramers;
carbazole derivatives;

The hole transport layer 4 may be formed by using the above materials alone, or may be formed by mixing them with other materials. In addition, it has a structure in which layers formed independently are laminated, a structure in which layers formed by mixing are laminated, or a layer formed by mixing with layers formed independently is laminated. good too. Organic layers other than the hole transport layer can also have a similar structure.

Alternatively, a coating type polymer material such as poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(styrene sulfonate) (PSS) may be used to form a hole injection layer/hole transport layer. can be done.

In addition to the materials normally used for the hole transport layer, P-doped trisbromophenylamine hexachloroantimony, radialene derivatives (WO2014/009310) and the like, and the structure of benzidine derivatives such as TPD are added to the partial structure. It is possible to use a polymer compound having

<Electron blocking layer>
The indenocarbazole compound of the present invention can be suitably used for the electron blocking layer 5 . In addition, for example, a compound having a known electron blocking action exemplified below can be used.
Carbazole derivatives such as 4,4′,4″-tri(N-carbazolyl)triphenylamine (
TCTA),
9,9-bis[4-(carbazol-9-yl)phenyl]fluorene,
1,3-bis(carbazol-9-yl)benzene (mCP),
2,2-bis(4-carbazol-9-ylphenyl)adamantane (Ad-Cz);
triarylamine compounds having a triphenylsilyl group, such as 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene;
Monoamine compounds with high electron blocking properties;
various triphenylamine dimers;

<Light emitting layer>
The indenocarbazole compound of the present invention can be suitably used for the light-emitting layer 6 . Moreover, you may use a well-known light emitting material. Examples of known luminescent materials include PIC-TRZ (see Non-Patent Document 1), CC2TA (see Non-Patent Document 2), PXZ-TRZ (see Non-Patent Document 3), and carbazolyldicyanobenzene (CDCB) derivatives such as 4CzIPN. (see Non-Patent Document 4); various metal complexes such as metal complexes of quinolinol derivatives such as tris(8-hydroxyquinoline) aluminum (Alq ₃ ); benzonitrile derivatives; anthracene derivatives; Styrylbenzene derivatives; pyrene derivatives; oxazole derivatives; polyparaphenylenevinylene derivatives; and the like can be used.
When an organic EL element has a light-emitting layer formed using a delayed fluorescence material, the organic EL element emits delayed fluorescence when current is applied.

The light-emitting layer 6 is preferably composed of a host material and a dopant material.
As the host material, in addition to the indenocarbazole compound of the present invention and a light-emitting material other than the delayed fluorescence material described above, benzonitrile derivatives, mCP, mCBP, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, and the like can be used.
As dopant materials, delayed fluorescence materials including benzonitrile derivatives, PIC-TRZ, CC2TA, PXZ-TRZ, 4CzIPN and other CDCB derivatives; quinacridone, coumarin, rubrene, anthracene, perylene and their derivatives; benzopyran derivatives; rhodamine Derivatives; aminostyryl derivatives; and the like can be used.

It is also possible to use a phosphorescent emitter as the luminescent material. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. Specifically, green phosphorescent emitters such as Ir(ppy) ₃ ; blue phosphorescent emitters such as FIrpic and FIr6; red phosphorescent emitters such as _Btp2Ir (acac) and Ir(piq) ₃ ; is used.

As a host material at this time, the indenocarbazole compound of the present invention or a heterocyclic compound having an indole ring can be used.
Further, for example, the following hole-injecting/hole-transporting host materials can be used.
Carbazole derivatives such as 4,4′-di(N-carbazolyl)biphenyl (CBP), TCTA
, mCP;
Furthermore, for example, the following electron-transporting host materials can be used.
p-bis(triphenylsilyl)benzene (UGH2),
2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBI);
By using such a host material, a high-performance organic EL device can be produced.

In order to avoid concentration quenching, doping of the phosphorescent emitter into the host material is preferably carried out by co-evaporation in the range of 1 to 30% by weight with respect to the entire emitting layer.

The light-emitting layer is preferably formed using the indenocarbazole compound or the delayed fluorescent material of the present invention, and more preferably formed using the delayed fluorescent material.

Further, when the light-emitting layer is produced using the indenocarbazole compound of the present invention, another light-emitting layer produced using a compound having a different work function as a host material is laminated adjacent to the light-emitting layer. be able to.

<Hole blocking layer>
A compound having a known hole blocking effect can be used for the hole blocking layer 7 . Known compounds having hole-blocking activity include phenanthroline derivatives such as bathocuproine (BCP); metals of quinolinol derivatives such as aluminum (III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq); complexes; dibenzothiophene derivatives such as 2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT); benzonitrile derivatives; various rare earth complexes; can. These materials may also serve as materials for the electron transport layer.

<Electron transport layer>
A known electron-transporting material can be used for the electron-transporting layer 8 . Examples of known electron-transporting materials include various metal complexes such as metal complexes of quinolinol derivatives such as Alq ₃ and BAlq; triazole derivatives; benzonitrile derivatives; triazine derivatives; oxadiazole derivatives; pyridine derivatives; benzotriazole derivatives; carbodiimide derivatives; quinoxaline derivatives; pyridoindole derivatives; phenanthroline derivatives; silole derivatives;

Further, a material that is N-doped with a metal such as cesium, a triarylphosphine oxide derivative (WO2014/195482), or the like can be used for the material normally used for the electron transport layer.

<Electron injection layer>
An electron injection layer 9 may be provided on the electron transport layer 8 . As the electron injection layer 9, alkali metal salts such as lithium fluoride and cesium fluoride; alkaline earth metal salts such as magnesium fluoride; metal oxides such as aluminum oxide; In a preferred choice of cathode and cathode this can be omitted.

In addition, a material that is normally used for the electron injection layer may be N-doped with a metal such as cesium, a triarylphosphine oxide derivative (WO2014/195482), or the like.

<Cathode>
As the cathode 10, an electrode material with a low work function such as aluminum, or an alloy with a lower work function such as a magnesium-silver alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy is used as the electrode material.

Hereinafter, the embodiments of the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

<Example 1: Compound 1>
7-(12,12-dimethyl-indeno[2,1-b]carbazol-10-yl)-10-phenyl-12,12-dimethyl-indeno[2,1-
b] Synthesis of carbazole;
In a reaction vessel purged with nitrogen,
100 mL of xylene,
7-bromo-10-phenyl-12,12-dimethyl-indeno [2,1-b]carbazole 5.0 g,
7,7-dimethyl-indeno[2,1-b]carbazole
3.6 g,
1.6 g of sodium t-butoxy,
0.2 g of t-butylphosphine and 0.1 g of palladium acetate
was added and heated, and stirred at 120° C. for 5 hours to obtain a reaction solution. After allowing the reaction solution to cool to room temperature, water was added and an extraction operation using toluene was performed. The collected organic layer was concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane). As a result, compound 1 was obtained as a white solid (83% yield).

The structure of the resulting white solid was identified using NMR. This ¹ H-NMR chart is shown in FIG. ¹ H-NMR (CDCl ₃ ) detected the following 36 hydrogen signals.
δ (ppm) = 8.49 (1H)
8.44 (1H)
8.41 (1H)
8.24 (1H)
7.88 (1H)
7.81 (1H)
7.78-7.67 (4H)
7.64-7.52 (3H)
7.49-7.23 (11H)
1.54 (6H)
1.49 (6H)

<Example 2: Compound 2>
Synthesis of 7-(carbazol-9-yl)-10-phenyl-12,12-dimethyl-indeno[2,1-b]carbazole;
In a reaction vessel purged with nitrogen,
100 mL of xylene,
7-bromo-10-phenyl-12,12-dimethyl-indeno [2,1-b]carbazole 6.0 g,
2.5 g of carbazole,
2.0 g of sodium t-butoxy,
0.2 g of t-butylphosphine and 0.1 g of palladium acetate
was added and heated, and stirred at 120° C. for 5 hours to obtain a reaction solution. After allowing the reaction solution to cool to room temperature, water was added and an extraction operation using toluene was performed. The collected organic layer was concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane). As a result, a white solid compound 2 was obtained (60% yield).

The structure of the resulting white solid was identified using NMR. This ¹ H-NMR chart is shown in FIG. ¹ H-NMR (CDCl ₃ ) detected the following 28 hydrogen signals.
δ (ppm) = 8.41 (1H)
8.34 (1H)
8.19 (2H)
7.80 (1H)
7.75-7.68 (4H)
7.62-7.50 (3H)
7.48-7.39 (6H)
7.39-7.25 (4H)
1.53 (6H)

<Example 3: Compound 3>
7-(carbazol-9-yl)-10-(biphenyl-4-yl)-
Synthesis of 12,12-dimethyl-indeno[2,1-b]carbazole;
In a reaction vessel purged with nitrogen,
50 mL of toluene,
7-bromo-10-(biphenyl-4-yl)-12,12-dimethyl-indeno[2,1-b]carbazole 3.0 g,
1.1 g of carbazole,
0.7 g of sodium t-butoxy,
0.1 g of t-butylphosphine and 0.1 g of palladium acetate
was added and heated, and stirred at 110° C. for 5 hours to obtain a reaction solution. After allowing the reaction solution to cool to room temperature, water was added and an extraction operation using toluene was performed. The collected organic layer was concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane). As a result, a white solid of Compound 3 (yield 56%) was obtained.

The structure of the resulting white solid was identified using NMR. This ¹ H-NMR chart is shown in FIG. ¹ H-NMR (CDCl ₃ ) detected the following 32 hydrogen signals.
δ (ppm) = 8.42 (1H)
8.35 (1H)
8.20 (2H)
7.96-7.88 (2H)
7.84-7.73 (5H)
7.63 (1H)
7.59-7.48 (4H)
7.48-7.26 (10H)
1.55 (6H)

<Example 4: Compound 24>
Synthesis of 7,10-bis(2-dibenzofuranyl)-10H,12H-12,12-dimethyl-indeno[2,1-b]carbazole;
In a reaction vessel purged with nitrogen,
70 mL of xylene,
2-bromo-dibenzofuran 1.8 g,
7-(2-dibenzofuranyl)-10H,12H-12,12-dimethyl-indeno[2,1-b]carbazole 3.0 g,
t-butoxy sodium 1.0 g,
0.1 g of t-butylphosphine and 0.3 g of palladium acetate
was added and heated, and stirred at 130° C. for 11 hours to obtain a reaction solution. After allowing the reaction solution to cool to room temperature, water was added and an extraction operation using toluene was performed. The collected organic layer was concentrated to obtain a crude product. The crude product was purified by column chromatography (carrier: silica gel, eluent: toluene/hexane). As a result, a white solid compound 24 was obtained (30% yield).

The structure of the resulting white solid was identified using NMR. This ¹ H-NMR chart is shown in FIG. ¹ H-NMR (CDCl ₃ ) detected the following 29 hydrogen signals.
δ (ppm) = 8.56 (1H)
8.51 (1H)
8.30 (1H)
8.29 (1H)
8.20 (1H)
8.06 (1H)
8.00-7.84 (3H)
7.73-7.67 (4H)
7.61 (1H)
7.56 (1H)
7.49 (1H)
7.44-7.39 (6H)
7.29 (1H)
1.52 (6H)

The glass transition point of the compound obtained in each example was determined using a high-sensitivity differential scanning calorimeter (DSC3100S, manufactured by Bruker AXS).
Glass transition point (°C)
Compound 1 of Example 1 189.3
Compound 2 of Example 2 143.2
Compound 3 of Example 3 160.1
Compound 24 of Example 4 147.7
It was found that the indenocarbazole compound of the present invention has a glass transition point of 100° C. or higher and is stable in a thin film state.

Using the compound obtained in each example, a vapor deposition film having a thickness of 100 nm was prepared on an ITO substrate, and the work function was measured with an ionization potential measuring device (manufactured by Sumitomo Heavy Industries, Ltd., model PYS-202). It was measured.
work function (eV)
Compound 1 of Example 1 5.79
Compound 2 of Example 2 5.94
Compound 3 of Example 3 5.86
Compound 24 of Example 4 5.81
The indenocarbazole compound of the present invention exhibits a favorable energy level compared to the work function of 5.5 eV of general hole-transporting materials such as NPD and TPD, and has good hole-transporting properties. I found out that I do.

<Device Example 1>
As shown in FIG. 5, a hole-injecting layer 3, a hole-transporting layer 4, an electron-blocking layer 5, a light-emitting layer 6, and a hole-blocking layer were formed on a glass substrate 1 on which an ITO electrode was previously formed as a transparent anode 2. A layer 7, an electron transport layer 8, an electron injection layer 9, and a cathode (aluminum electrode) 10 were deposited in this order to prepare an organic EL device emitting delayed fluorescence.

正孔注入層３の上に、下記構造式で表されるＨＴＭ－１を蒸着し、膜厚２５ｎｍの正孔輸送層４を形成した。

正孔輸送層４の上に、実施例１の化合物１を蒸着し、膜厚５ｎｍの電子阻止層５を形成した。

電子阻止層５の上に、ドーパント材料として下記構造式で表されるＥＭＤ－１（４ＣｚＩＰＮ）とホスト材料として下記構造式で表されるＥＭＨ－１（ｍＣＢＰ）とを、蒸着速度比がＥＭＤ－１：ＥＭＨ－１＝１５：８５となる蒸着速度で二元蒸着し、膜厚３０ｎｍの発光層６を形成した。
なお、ＥＭＤ－１は熱活性化遅延蛍光材料である。

発光層６の上に、下記構造式で表されるＥＴＭ－１を蒸着し、膜厚１０ｎｍの正孔阻止層７を形成した。

正孔阻止層７の上に、下記構造式で表されるＥＴＭ－２を蒸着し、膜厚４０ｎｍの電子輸送層８を形成した。

電子輸送層８の上に、フッ化リチウムを蒸着し、膜厚１ｎｍの電子注入層９を形成した。
最後に、電子注入層９の上にアルミニウムを蒸着し、膜厚１００ｎｍの陰極１０を形成した。 Specifically, after cleaning the glass substrate 1 with an ITO film having a thickness of 150 nm with an organic solvent, the surface was cleaned by UV ozone treatment. After that, this glass substrate with ITO electrodes was mounted in a vacuum deposition machine, and the pressure was reduced to 0.001 Pa or less.
Subsequently, a compound HIM-1 having the following structural formula was vapor-deposited so as to cover the transparent anode 2 to form a hole injection layer 3 having a thickness of 10 nm.

HTM-1 represented by the following structural formula was deposited on the hole injection layer 3 to form a hole transport layer 4 with a thickness of 25 nm.

Compound 1 of Example 1 was deposited on the hole transport layer 4 to form an electron blocking layer 5 with a thickness of 5 nm.

On the electron blocking layer 5, EMD-1 (4CzIPN) represented by the following structural formula as a dopant material and EMH-1 (mCBP) represented by the following structural formula as a host material are deposited. Binary vapor deposition was performed at a vapor deposition rate of 1:EMH-1=15:85 to form a light-emitting layer 6 having a thickness of 30 nm.
EMD-1 is a thermally activated delayed fluorescence material.

ETM-1 represented by the following structural formula was vapor-deposited on the light-emitting layer 6 to form a hole-blocking layer 7 having a thickness of 10 nm.

ETM-2 represented by the following structural formula was vapor-deposited on the hole-blocking layer 7 to form an electron-transporting layer 8 having a thickness of 40 nm.

Lithium fluoride was deposited on the electron transport layer 8 to form an electron injection layer 9 with a thickness of 1 nm.
Finally, aluminum was deposited on the electron injection layer 9 to form a cathode 10 with a film thickness of 100 nm.

<Device Example 2>
An organic EL device emitting delayed fluorescence was produced under the same conditions as in Device Example 1, except that the compound 2 of Example 2 was used in place of the compound 1 of Example 1 to form the electron blocking layer 5 .

<Device Example 3>
An organic EL device emitting delayed fluorescence was produced under the same conditions as in Device Example 1, except that Compound 3 of Example 3 was used in place of Compound 1 of Example 1 to form the electron blocking layer 5 .

<Device Example 4>
An organic EL device emitting delayed fluorescence was fabricated under the same conditions as in Device Example 1, except that the compound 24 of Example 4 was used in place of the compound 1 of Example 1 to form the electron blocking layer 5 .

<Element Comparative Example 1>
An organic EL device emitting delayed fluorescence was produced under the same conditions as in Device Example 1, except that HTM-A of the following structural formula was used in place of Compound 1 of Example 1 to form the electron blocking layer 5. .

The characteristics of the organic EL devices produced in Device Examples 1 to 4 and Device Comparative Example 1 were measured in air at room temperature. Table 1 shows the measurement results of the emission characteristics when a DC voltage was applied to the fabricated organic EL device.

Using the organic EL devices produced in Device Examples 1 to 4 and Device Comparative Example 1, the device life was measured. Specifically, when the light emission luminance (initial luminance) at the start of light emission is 1000 cd/m ² and constant current driving is performed, the light emission luminance is 950 cd/m ² (equivalent to 95% when the initial luminance is 100%). : 95% attenuation) was measured. Table 1 shows the results.

Regarding the luminance when a current with a current density of 10 mA/cm ² was applied, the device comparative example 1 had a luminance of 4653 cd/m ² , while the device examples 1 to 4 exhibited a high luminance of 4662 to 5375 cd/m ² . was brightness.

The luminous efficiency was 46.6 cd/A in Device Comparative Example 1, whereas it was 46.7 to 53.8 cd/A in Device Examples 1 to 4, which were all high efficiencies.

The power efficiency was 27.0 lm/W in Device Comparative Example 1, whereas it was 27.0 to 29.6 lm/W in Device Examples 2 to 4, which was equal to or higher than the efficiency.

The element life (95% attenuation) was 151 hours in the element comparative example 1, whereas it was 240 hours in the element example 1, which was greatly prolonged.

It was confirmed that the voltage when a current with a current density of 10 mA/cm ² was applied was equivalent to that of device examples 1 to 4 and device comparative example 1.

From the above results, the organic EL device using the indenocarbazole compound of the present invention in the electron blocking layer and using the thermally activated delayed fluorescent material as the dopant material in the light emitting layer is an organic EL device using the known HTM-A. It has been found that, compared with EL devices, the luminous efficiency and luminance are high, and depending on the structure of the indenocarbazole compound, the power efficiency is high or the life is long.

In addition, Device Example 1 and Device Example 2, in which the electron blocking layer 5 was formed using the indenocarbazole compound having the same structure except for X in Formula (1), were compared. As a result, when X is an indenocarbazolyl group, element example 1 using compound 1 having two indenocarbazole structures in the molecule used compound 2 in which X is a carbazolyl group. The life of the device was much longer than that of device example 2.

Similarly, Device Example 2 and Device Example 3, in which the electron blocking layer 5 was formed using the indenocarbazole compound having the same structure except for R ¹ in Formula (1), were compared. As a result, it was found that Element Example 2 using compound 2 in which R ¹ is a phenyl group, which is an aromatic hydrocarbon group having one aromatic ring, has an aromatic hydrocarbon group in which R ¹ has two or more aromatic rings. The luminance and luminous efficiency were higher and the life was longer than that of Device Example 3 using Compound 3 having a biphenylyl group which is a hydrogen group.

Furthermore, Device Examples 1 to 3 and Device Examples in which the electron blocking layer 5 was formed using an indenocarbazole compound that differs in whether or not X and R ¹ in formula (1) are an oxygen-containing aromatic heterocyclic group. compared with 4. As a result, element examples 1 to 3 using compounds 1 to 3 in which X and R ¹ are not an oxygen-containing aromatic heterocyclic group were found to be better than compound 24 in which X and R ¹ are an oxygen-containing aromatic heterocyclic group. The life of the element was longer than that of Example 4 using . On the other hand, Device Example 4 was superior to Device Examples 1 to 3 in luminance, luminous efficiency and power efficiency.

As described above, the indenocarbazole compound of the present invention has a hole-transporting property, an excellent electron-blocking property, and a stable thin film state, and is therefore excellent as a compound for organic EL devices. The organic EL device of the present invention produced using this compound has high luminous efficiency and high brightness. Therefore, for example, it is possible to develop it for use in home electric appliances and lighting.

1 glass substrate 2 transparent anode 3 hole injection layer 4 hole transport layer 5 electron blocking layer 6 light emitting layer 7 hole blocking layer 8 electron transport layer 9 electron injection layer 10 cathode

Claims (4)

A material for an organic electroluminescence element constituting a hole transport layer, a hole injection layer or an electron blocking layer of an organic electroluminescence element using a delayed fluorescence material as a dopant material in the light emitting layer ,
Having a hole-transport property and containing an indenocarbazole compound represented by the following general formula (1),
Materials for organic electroluminescence devices.

During the ceremony,
R ¹ represents a phenyl group, a biphenylyl group or a dibenzofuranyl group, R ² to R ¹² may be the same or different, hydrogen atom; deuterium atom; fluorine atom; chlorine atom; cyano group; nitro group; C1-8 alkyl group; C5-10 cycloalkyl group; C2-6 alkenyl group; C1-6 alkyloxy group; C5-10 cycloalkyloxy group; an aromatic hydrocarbon group; an aromatic heterocyclic group; an aryloxy group; or ^{a disubstituted} amino group substituted with an aromatic hydrocarbon group or an aromatic heterocyclic group; Alternatively, they may be bonded through an unsubstituted methylene group, an oxygen atom or a sulfur atom to form a ring, and R ¹ does not contain a triazinyl group.
X represents an unsubstituted carbazolyl group or an unsubstituted dibenzofuranyl group , and when X is a nitrogen-containing aromatic heterocyclic group, it is bonded via an N atom. The indenocarbazole compound is represented by the following general formula (1-1),
2. The material for organic electroluminescence elements according to claim 1.

During the ceremony,
R ¹ to R ¹² and X have the same meanings as described in formula (1) above. 2. The material for an organic electroluminescence device according to claim 1, wherein the alkyl group having 1 to 8 carbon atoms represented by R ² to R ¹² is an alkyl group having 1 to 6 carbon atoms. In an organic electroluminescence device having a light-emitting layer and another layer between a pair of electrodes,
the other layer is a hole injection layer, a hole transport layer or an electron blocking layer;
The organic electroluminescence element material according to claim 1 is used as a constituent material of the other layer,
An organic electroluminescence device , wherein a delayed fluorescence material is used as a dopant material in the light emitting layer .

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